Downhole plug assemblies with collet adapters and methods thereof

ABSTRACT

Downhole plug assemblies comprising plug, release sleeve and collet adapter and methods thereof are disclosed. The plug comprises of a mandrel with a bore and an outer subassembly comprising a top element, anchoring system, sealing system and a nose element. The release sleeve is engaged and secured within the bore at a proximal portion by a plurality of shearable fastening members. The collet adapter comprises of a plurality of fingers with each finger ending in a head at the tip. The collet head is engaged with a slanting face of the release sleeve at a lower end and is configured to be engaged with a setting tool at an upper end. During the release process, the fingers expand to prevent disengaging from the face thus transferring the load to the release sleeve and causing the fastening members to shear off and the release sleeve to release from the mandrel.

TECHNICAL FIELD

The present disclosure generally relates to tools used for isolation in well bores. More particularly, the present disclosure relates to downhole plug assemblies with collet adapters and methods thereof.

BACKGROUND

Technological innovations in the oil and gas industry are primarily focused on the Exploration and Production (E & P) business. Due to low permeability in the shale rocks and tight sands deep under the ground, it is extremely difficult to drill and stimulate production of crude oil otherwise popularly known as “black gold”. Hence the unconventional directional drilling associated with the Plug and Perf operations and the hydraulic fracturing process has been getting popularity from the wildcat wells to promising drill pads. Composite materials have replaced metals in various engineering applications owing to their numerous advantages, like high strength/weight ratio and other better physical properties. Due to these advantages, there has been an increasing demand for use of these materials in manufacturing frac plugs. Due to its lesser weight, the plug can be deployed with a faster speed, in addition, the milling time could be lesser compared to the metal based frac plugs.

Hydraulic fracturing has been of late getting lots of interests in the gas exploration and production process. It is a gas well stimulation and extraction technique designed for areas underlain by large shale formations found a mile or more below the ground surface.

Frac/Bridge plugs are deployed deep under the ground after the casing has already cemented in place. They are set at appropriate chosen locations using Baker #10 or Baker #20 setting tool, depending on the casing size and plug size. In the conventional prior art setting process, generally the plugs are set either by shearing the thread or by shearing the pins. Threads are either sheared externally or internally with respect to the mandrel. An axial force is applied to a composite mandrel in direction parallel to the axis of its bore, during which the elastomer seals the casing followed by slips biting the casing.

Conventional methods of installing the plugs onto the setting tool typically involve fastening the setting sleeve and the adapter to the plug by screws on the rig floor. Given the number of plugs (about 50 to 200 plugs per perf & frac operation in each well) used in the hydraulic fracturing process, this installing process itself becomes time consuming.

In the light of aforementioned discussion, there is a need for downhole plug assemblies which require lesser time for installation and are easier to install as well. The present invention discloses downhole plug assemblies with collet mechanisms that are easier and faster to install onto the setting tool and methods thereof. A collet adapter attached to the setting tool simply snaps onto a release sleeve of the downhole plug assembly during the installation on the rig floor without any need for fastening the plug with the setting tool by means of screws thus saving time. Further, after the downhole setting of the plugs, shearable screws coupling the release sleeve with the mandrel of the plug shear off during the release process without leaving any debris within the bore of the plug. Another advantage of the present invention is that the fiber composite mandrel does not experience substantial internal stress or does not need to have a high tensile strength, like that of the other plugs that undergo conventional shearing methods. Thus, the fiber composite mandrel need not be manufactured exclusively by filament winding process but can be made by a simple economical process.

BRIEF SUMMARY

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

Exemplary embodiments of the present disclosure are directed towards downhole plug assemblies. The downhole plug assembly comprises of a plug, an annular release sleeve and a collet adapter. The plug comprises of a substantially cylindrical central mandrel and a substantially cylindrical hollow outer subassembly disposed circumferentially around the central mandrel. The mandrel has a proximal portion configured to be oriented up hole, a distal portion configured to be oriented downhole and a substantially longitudinal bore. The proximal portion has a plurality of apertures disposed circumferentially, the apertures extending perpendicular to the longitudinal axis of the bore and being engaged with shearable fastening members. The outer subassembly comprises of an annular top element that is disposed circumferentially around the proximal portion, one or more of anchoring system disposed circumferentially around the mandrel for securely engaging the plug with a casing in a well bore, an expandable sealing system disposed circumferentially around the mandrel for sealing the gap between an outer surface of the plug and the casing and an annular nose element disposed circumferentially around the distal portion.

The release sleeve has a first end that is configured to be oriented up hole and a second end configured to be oriented downhole. The release sleeve has a constant outer diameter and a progressively tapering inner diameter with the inner diameter at the second end being lesser than the inner diameter at the first end. The release sleeve has an external and an internal surface with the external surface having a lesser length than the internal surface. The second end has a slanting face sloping towards the first end. The release sleeve has one or more receiving members that are configured for receiving and engaging a plurality of shearable fastening members. The release sleeve is releasably engaged and secured within the bore at the proximal portion by a plurality of the shearable fastening members. The release sleeve engaged with the plug forms a plug subassembly.

The collet adapter has an upper end that is configured to be oriented up hole and a lower end that is configured to be oriented downhole. The collet adapter is configured to be an adapter between a setting tool and the plug subassembly. The upper end is configured to be engaged with the setting tool. The lower end has a plurality of fingers separated by slots with each finger ending in a head at the tip. The collet adapter is slidable through the progressively tapering inner diameter of the release sleeve to compress and then snap into an engaging position where a lower surface of each head engages the face. The collet fingers are radially expandable to securely engage the sloping face upon application of a predetermined load greater than a predetermined setting load thus transferring the load to the release sleeve and then to the shearable fastening members causing the fastening members to shear and the release sleeve to release from the mandrel.

Other exemplary embodiments of the present subject matter are directed towards methods for installing, setting and releasing a plug for isolation in a well bore. The method begins with the step of providing a plug subassembly comprising a plug and an annular release sleeve. The plug and release sleeve have a conformation as described in the previous paragraphs. This is followed by providing a collet adapter with a conformation as described in the previous paragraphs. The next step is to install the plug subassembly onto the setting tool by sliding the collet adapter through the progressively tapering inner diameter of the release sleeve thus compressing and snapping the collet adapter into an engaging position wherein a lower surface of each head engages the slanting face of the release sleeve. This is followed by deploying the downhole plug subassembly engaged with the setting tool downhole to a predetermined location. Then a setting sleeve that is engaged with a setting tool at a first end and the top element at the second end is actuated with a predetermined setting load. This pushes the top element and sets the plug, wherein the anchoring system engages the plug with the casing and the sealing system seals the gap between the outer surface of the plug and the casing. Finally a predetermined load greater than the setting load is applied thus pulling the collet adapter. The collet fingers radially expand to securely engage the sloping face thereby transferring the load to the release sleeve and then to the shearable fastening members causing the fastening members to shear and the release sleeve thereof to release from the mandrel.

It is an object of the present invention to disclose downhole plug assemblies that are easier and faster to install onto the setting tool. For installing this plug assembly there is no need for threading or securing with set screws or for any special tool. A simple push with bare hands is enough to snap the collet adapter in place for installation. Thus the set up time on the rig floor is highly reduced.

It is another object of the present invention to disclose downhole plug assemblies that do not leave any debris within the bore of the plugs during the release process. The sheared debris will be pulled up to the ground along with the setting tool. A clean borehole is left behind for the free flow of material or for the frac ball to seat.

It is another object of the present invention to disclose downhole plug assemblies with fiber composite plugs that need not have a high tensile strength since the plug material itself does not undergo shearing during the release process.

It is another object of the present invention to disclose robust collet adapters that can be reused multiple times as it is never loaded beyond its strength.

Furthermore, the objects and advantages of this invention will become apparent from the following description and the accompanying annexed drawings.

BRIEF DESCRIPTION OF DRAWINGS

Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, in conjunction with the accompanying drawings, wherein like reference numerals have been used to designate like elements, and wherein:

FIG. 1 is a schematic representation of a part sectional view of a downhole plug assembly engaged with a setting sleeve, in accordance with a non limiting exemplary embodiment of the present disclosure.

FIG. 2 is a schematic representation of an exploded, partially cut-away view of the downhole plug assembly and the setting sleeve depicted in FIG. 1.

FIG. 3 is a schematic representation of a longitudinal section of a downhole plug assembly, in accordance with a non limiting exemplary embodiment of the present disclosure.

FIG. 4 is a schematic representation of a longitudinal section of a downhole plug assembly, in accordance with another non limiting exemplary embodiment of the present disclosure.

FIG. 5 is a schematic representation of an enlarged view of a portion of the downhole plug assembly shown in FIG. 3 depicting the engagement of the collet adapter with the release sleeve.

FIG. 6 is a schematic representation of an isometric view of a shearable screw, in accordance with a non limiting exemplary embodiment of the present disclosure.

FIG. 7 is a schematic representation of an isometric view of a collet adapter, in accordance with a non limiting exemplary embodiment of the present disclosure.

FIG. 8A is a schematic representation of an isometric, partially cut-away view of a release sleeve, in accordance with a non limiting exemplary embodiment of the present disclosure.

FIG. 8B is a schematic representation of an isometric, partially cut-away view of a release sleeve, in accordance with another non limiting exemplary embodiment of the present disclosure.

FIG. 9 is a schematic representation of an exploded, partially cut-away view of a plug subassembly, in accordance with a non limiting exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The use of “including”, “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. Further, the use of terms “first”, “second”, and “third”, and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

According to different non limiting exemplary embodiments of the present disclosure, downhole plug assemblies for oil and gas wellbores are disclosed.

In accordance with different non limiting exemplary embodiments of the present subject matter, methods for installing, setting and releasing plugs for isolation in oil and gas well bores are disclosed.

Referring to FIGS. 1-5 and 9, they depict different views of downhole plug assemblies and plug subassembly. Referring to FIGS. 7, 8A and 8B, they depict different views of collet adapter and release sleeves.

The downhole plug assembly 100 comprises of a plug 102, an annular release sleeve 108 and a collet adapter 112. The plug 102 comprises of a substantially cylindrical central mandrel 104 and a substantially cylindrical hollow outer subassembly 106 disposed circumferentially around the central mandrel 104. The mandrel 104 has a proximal portion 962 configured to be oriented up hole, a distal portion 964 configured to be oriented downhole and a substantially longitudinal bore 116. The proximal portion 962 has a plurality of apertures 128 disposed circumferentially, the apertures 128 extending perpendicular to the longitudinal axis of the bore 116 and being engaged with shearable fastening members. The outer subassembly 106 comprises of an annular top element 118 that is disposed circumferentially around the proximal portion 962, one or more of anchoring system disposed circumferentially around the mandrel 104 for securely engaging the plug 102 with a casing in a well bore, an expandable sealing system disposed circumferentially around the mandrel 104 for sealing the gap between an outer surface 107 of the plug 102 and the casing and an annular nose element 124 disposed circumferentially around the distal portion 964. The plug is preferably made of fiber composite material though metal plugs or plugs made partly of metal and partly of composite material can also be used in the assembly without limiting the scope of the present disclosure.

The release sleeve 108 has a first end 144 that is configured to be oriented up hole and a second end 146 that is configured to be oriented downhole. The release sleeve 108 has a constant outer diameter and a progressively tapering inner diameter with the inner diameter at the second end 146 being lesser than the inner diameter at the first end 144. The release sleeve 108 has an external 140 and an internal surface 142 with the external surface 140 having a lesser length than the internal surface 142. The second end 146 has a slanting face 132 sloping towards the first end 144. The release sleeve 108 has one or more receiving members that are configured for receiving and engaging a plurality of shearable fastening members. The receiving member can be a blind hole, a through hole or a circumferential groove without limiting the scope of the present disclosure. The release sleeve 108 is releasably engaged and secured within the bore 116 at the proximal portion 962 by a plurality of the shearable fastening members. The release sleeve engaged with the plug forms a plug subassembly.

The collet adapter 112 has an upper end 156 that is configured to be oriented up hole and a lower end 158 that is configured to be oriented downhole. The collet adapter 112 is configured to be an adapter between a setting tool and the plug subassembly. The upper end 156 is configured to be engaged with the setting tool. The lower end 158 has a plurality of fingers 138 separated by slots 160 with each finger 138 ending in a head 136 at the tip. The collet adapter 112 is slidable through the progressively tapering inner diameter of the release sleeve 108 to compress and then snap into an engaging position where a lower surface 134 of each head 136 engages part of the face 132. The collet fingers 138 are radially expandable to securely engage the sloping face 132 upon application of a predetermined load greater than a predetermined setting load thus transferring the load to the release sleeve 108 and then to the shearable fastening members causing the fastening members to shear and the release sleeve 108 to release from the mandrel 104. In some embodiments, the collet adapters are made of alloy steel though collet adapters made of any other suitable material with sufficient strength can also be used without limiting the scope of the present disclosure.

In some embodiments, the shearable fastening members that engage the mandrel and the release sleeve are shearable screws, though any other shearable fastening members such as pins can be used without limiting the scope of the present disclosure. In some embodiments, the shearable fastening members are made of brass though fastening members made of steel alloy, fiberglass or any other suitable material that can shear upon application of predetermined load can also be used without limiting the scope of the present disclosure. The choice of the material depends on strength requirements also. In some embodiments, the number of shearable fastening members used to engage the mandrel with the release sleeve is eight but the number can vary depending on the shear force used to set the plug. In other words, the shear load can be varied as per requirement by altering the number of screws used to hold the release sleeve within the mandrel.

In some embodiments, the plug further comprises of anti-preset means to prevent the plug from setting prior to the application of a predetermined setting load. The anti-preset means are one or more of shearable fastening members such as screws that shear off upon application of a predetermined setting load.

Referring specifically to FIGS. 1 and 2, they depict different views of a downhole plug assembly engaged with a setting sleeve 114. Here a frac plug 102 is connected to a setting tool by means of a collet adapter 112 and the setting sleeve 114. A setting sleeve and an adapter are used widely in the oilfield industry to connect plugs to their setting tools. Here, a set of eight shear screws 110 are used to hold a release sleeve 108 within the bore 116 of the mandrel 104 of the frac plug 102. The collet adapter 112 snaps into place on the inner profile of this frac plug 102. The setting sleeve 114 connects the setting tool to the top element of the outer subassembly 106. The setting sleeve 114 engages the setting tool at a top end 103 and the top element at a bottom end 105.

Referring specifically to FIG. 3, the longitudinal bore 116 has a conical feature 117 defined for seating a frac ball. The bore 116 is sealed when a ball is dropped and is seated on the tapered conical feature 117. During the setting process, the top element 118 at the proximal portion is pushed by the setting sleeve to initiate setting. The top element 118 is also connected to the mandrel 104 using three anti-preset screws 126 which prevent the frac plug from setting accidentally upon impact with debris downhole. Once a certain load value is crossed, the anti-preset screws 126 shear off and the top element 118 starts to stroke transferring the load to a first metal slip 120 a. Under load from the top element 118, the metal slip tries to ride up on the ramps of the first Gauge Ring 121 a. In an attempt to do so, the metal slips, break apart into many sections along weakened sections in its body. These sections are now free to ride up on the gauge ring ramps till they contact the outer well casing and bite into them. Simultaneously, the elastomeric element 122 which is the sealing system, under load from the gauge rings and metal slips, compresses and gets squeezed. It bulges outwards till it forms a tight seal with the casing. The same sequence of events happens on the other end of the frac plug. Since the bottom nose element 124 is threaded onto the distal portion of the mandrel 104, when the setting sleeve is pushing on the upper components of the frac plug, the collet adapter 112 holds on to the nose element 124 via the threads on the mandrel 104 and the shear screws 110 connecting the mandrel 104 to the release sleeve 108. This reaction force, acts from the bottom and causes the second metal slip 120 b to ride up on the second gauge ring 121 b ramp under load from the nose element 124. The first and second metal slips 120 a and b and the gauge rings 121 a and b together form the anchoring system. Both the nose element 124 and the top element 118 have an angled face contacting the metal slips so that when they are engaged and biting the casing, the angle supports their load. In this configuration, the plug is said to be set and needs to be separated from the setting tool which was used to set it.

Referring specifically to FIG. 4, it depicts a downhole plug assembly 200 with a bridge plug adapter 225 seated within the bore 216 of the mandrel 204 thus converting the plug into a bridge plug. The bridge plug adapter 225 is threadably engaged with an inner surface 223 of the mandrel 204. A lower end of the adapter 225 has means for fixing O rings 219 for effective sealing of the plug.

Referring specifically to FIG. 5, the mechanism for releasing the plug can be seen in clearer detail. Once the frac plug is set and the metal slips are biting into the casing, it is not possible for the setting sleeve to stroke further under pressure from the tool. Hence, any increased load beyond this point is realized in the form of an upward tension force on the collet adapter. The face 132 of the release sleeve 108 engaged by a lower surface 134 of the collet head 136 has a negative angle. So when the collet pulls against the release sleeve, the collet fingers 138 open up more and prevent it from disengaging. Hence the entire load from the collet adapter is transferred to the release sleeve 108 which in turn, loads up the shear screws. Under sufficient load from the collet, these screws shear off and thus release the release sleeve from the inner bore of the mandrel 104 and the full plug as well.

Referring to FIG. 6, it depicts a perspective view of a shearable screw 110 that couples the mandrel with the release sleeve. The sheared off screw 110 does not leave any debris in the inside bore of the mandrel. The lower portion of the screw 110 has threads 154 which engage with the threaded holes on the release sleeve. Above these threads 154 is the stem 152 that has the shear area which controls the value at which the frac plug is released from the tool. The shear screw head 148 prevents the sheared off part from falling into the well as it is secured to the mandrel using epoxy. The step 150 sits tightly in the hole of the mandrel, and causes the shear area to be under load and allows for the fine tuning of the shear value.

In some other embodiments, the shearable screw is threaded only at a top portion of the stem which is engaged with the aperture and the lower portion of the stem is unthreaded. In such cases, the inner surface of the aperture in the mandrel is accordingly configured to threadably engage the screw.

In some embodiments, the shearable fastening member is a pin fastener that engages the aperture of the mandrel and the receiving member of the release sleeve by adhesive means or tight fit.

Referring to FIG. 7, 8A and 8B, they depict detailed views of the collet adapter and the release sleeve along with their engagement profiles. The upper end 156 of the collet adapter 112 has a threaded configuration to connect to the setting tool. The lower end 158 of the adapter 112 has slots 160 cut into it to form several fingers 138. These fingers 138 act as cantilever beams and can flex radially. When the head 136 of the collet 112 is inserted into the tapered inner profile of the release sleeve 108, the collet fingers 138 flex inward radially and allow for the collet 112 to be inserted into the sleeve 108. Once it passes through the end of the sleeve the load on the flexed fingers 138 of the collet 112 are released and they snap into place to lock in position. The front face 132 of the release sleeve 108 has a negative angle to prevent the collet adapter 112 from disengagement. The release sleeve 108 has one or more receiving members for receiving and engaging shear screws. In some embodiments the receiving members are blind holes 130 as shown in FIG. 8A and in some embodiments the receiving member is a circumferential groove 830 on an external surface 840 of the release sleeve 808.

Referring specifically to FIG. 9, it shows an exploded and partially cut-away view of all the parts of a plug subassembly 900. The mandrel 104 is the central element upon which, the components of the outer subassembly are assembled in order. The top element 118, first metal slip 120 a, first gauge ring 121 a, elastomeric element 122, second gauge ring 121 b and second metal slip 120 b are all slid on one by one in the abovementioned sequence. In order to hold them all in place, the nose element 124 with a pump down ring feature is threaded onto distal portion 964 of the mandrel 104. The bottom most part of the mandrel 104 has a plurality of prongs whose purpose is to seat a frac ball from a frac plug lower in the well and allow flow past it. The release sleeve 108 is inserted into the bore at the proximal portion 962 and held in place using eight shear screws 110.

Other exemplary embodiments of the present subject matter are directed towards methods for installing, setting and releasing a plug for isolation in a well bore. The method begins with the step of providing a plug subassembly comprising a plug and an annular release sleeve. The plug and release sleeve have conformations as described in the previous paragraphs. This is followed by providing a collet adapter with conformations as described in the previous paragraphs. The next step is to install the plug subassembly onto the setting tool by sliding the collet adapter engaged with the setting tool through the progressively tapering inner diameter of the release sleeve thus compressing and snapping the collet adapter into an engaging position wherein a lower surface of each head engages the slanting face of the release sleeve. This is followed by deploying the downhole plug assembly engaged with the setting tool downhole to a predetermined location. Then a setting sleeve that is engaged with a setting tool at a top end and the top element at the bottom end is actuated with a predetermined setting load. This pushes the top element and sets the plug, wherein the anchoring system engages the plug with the casing and the sealing system seals the gap between the outer surface of the plug and the casing. Finally a predetermined load greater than the setting load is applied thus pulling the collet adapter. The collet fingers radially expand to securely engage the sloping face thereby transferring the load to the release sleeve and then to the shearable fastening members causing the fastening members to shear and the release sleeve thereof to release from the mandrel.

Although the present disclosure has been described in terms of certain preferred embodiments and illustrations thereof, other embodiments and modifications to preferred embodiments may be possible that are within the principles and spirit of the invention. The above descriptions and figures are therefore to be regarded as illustrative and not restrictive.

Thus the scope of the present disclosure is defined by the appended claims and includes both combinations and sub combinations of the various features described herein above as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description. 

We claim:
 1. A downhole plug assembly comprising: a plug comprising a substantially cylindrical central mandrel and a substantially cylindrical hollow outer subassembly, the outer subassembly thereof being disposed circumferentially around the mandrel, the mandrel thereof having a proximal portion and a distal portion and a substantially longitudinal bore, the proximal portion thereof being configured to be oriented up hole and the distal portion thereof being configured to be oriented downhole, the proximal portion thereof having a plurality of apertures disposed circumferentially, the aperture thereof extending therethrough perpendicular to the longitudinal axis of the bore and being engaged with a shearable fastening member, the outer subassembly thereof comprising an annular top element disposed circumferentially around the proximal portion, at least one of an anchoring system disposed circumferentially around the mandrel for securely engaging the plug with a casing in a well bore, an expandable sealing system disposed circumferentially around the mandrel for sealing the gap between an outer surface of the plug and the casing and an annular nose element disposed circumferentially around the distal portion; an annular release sleeve having a first end and a second end, the first end thereof being configured to be oriented up hole and the second end thereof being configured to be oriented downhole, the release sleeve thereof having an outer diameter and a progressively tapering inner diameter, the inner diameter at the second end thereof being lesser than the inner diameter at the first end thereof, the release sleeve thereof further having an external surface and an internal surface, each of the external surface and the internal surface having a length associated therewith, the length of the external surface being lesser than the length of the internal surface, the second end thereof having a slanting face sloping towards the first end, the release sleeve thereof further having at least one of a receiving member, the receiving member being configured for receiving and engaging a plurality of the shearable fastening members, the release sleeve thereof being releasably engaged and secured within the bore at the proximal portion by a plurality of the shearable fastening members, the release sleeve engaged with the plug forming a plug subassembly; and a collet adapter having an upper end and a lower end, the upper end thereof being configured to be oriented up hole and the lower end thereof being configured to be oriented downhole, the collet adapter being configured to be an adapter between a setting tool and the plug subassembly, the upper end thereof being configured to be engaged with the setting tool, the lower end thereof having a plurality of fingers separated by slots, each finger thereof ending in a head at the tip, the collet adapter being slidable through the progressively tapering inner diameter of the release sleeve to compress and then snap into an engaging position wherein a lower surface of each of the head engages the face, the fingers thereof configured to be radially expandable to securely engage the face upon application of a load greater than a setting load thereby transferring the load to the release sleeve and then to the shearable fastening members causing the fastening members thereof to shear off and the release sleeve thereof to release from the mandrel.
 2. The downhole plug assembly as claimed in claim 1, wherein the receiving member is a hole, the hole thereof extending therethrough perpendicular to the longitudinal axis of the bore.
 3. The downhole plug assembly as claimed in claim 1, wherein the receiving member is a circumferential groove on the external surface.
 4. The downhole plug assembly as claimed in claim 1, wherein the plug is a frac plug.
 5. The downhole plug assembly as claimed in claim 4, wherein the bore has a conical feature defined for seating a frac ball.
 6. The downhole plug assembly as claimed in claim 1, wherein the plug further comprises of a bridge plug adapter seated within the bore thus converting the plug into a bridge plug.
 7. The downhole plug assembly as claimed in claim 6, wherein the bridge plug adapter is threadably engaged with an inner surface of the mandrel.
 8. The downhole plug assembly as claimed in claim 1, wherein the plug is substantially made of composite material.
 9. The downhole plug assembly as claimed in claim 1, wherein the shearable fastening members engaging the mandrel with the release sleeve shear off without leaving any debris within the bore of the mandrel.
 10. The downhole plug assembly as claimed in claim 1, wherein the shearable fastening members are shearable screws.
 11. A method for installing, setting and releasing a plug for isolation in a well bore, the method comprising the steps of: a) providing a plug subassembly, the plug subassembly thereof comprising a plug and an annular release sleeve, the plug thereof comprising a substantially cylindrical central mandrel and a substantially cylindrical hollow outer subassembly, the outer subassembly thereof being disposed circumferentially around the mandrel, the mandrel thereof having a proximal portion and a distal portion and a substantially longitudinal bore, the proximal portion thereof being configured to be oriented up hole and the distal portion thereof being configured to be oriented downhole, the proximal portion thereof having a plurality of apertures disposed circumferentially, the aperture thereof extending therethrough perpendicular to the longitudinal axis of the bore and being engaged with a shearable fastening member, the outer subassembly thereof comprising an annular top element disposed circumferentially around the proximal portion, at least one of an anchoring system disposed circumferentially around the mandrel for securely engaging the plug with a casing in a well bore, an expandable sealing system disposed circumferentially around the mandrel for sealing the gap between an outer surface of the plug and the casing and an annular nose element disposed circumferentially around the distal portion, the release sleeve thereof having a first end and a second end, the first end thereof being configured to be oriented up hole and the second end thereof being configured to be oriented downhole, the release sleeve thereof having an outer diameter and a progressively tapering inner diameter, the inner diameter at the second end thereof being lesser than the inner diameter at the first end thereof, the release sleeve thereof further having an external surface and an internal surface, each of the external surface and the internal surface having a length associated therewith, the length of the external surface being lesser than the length of the internal surface, the second end thereof having a slanting face sloping towards the first end, the release sleeve further having at least one of a receiving member, the receiving member being configured for receiving and engaging a plurality of the shearable fastening members, the release sleeve thereof being releasably engaged and secured within the bore at the proximal portion by a plurality of the shearable fastening members; b) providing a collet adapter, the collet adapter thereof having an upper end configured to be oriented up hole and a lower end configured to be oriented downhole, the collet adapter thereof being configured to be an adapter between a setting tool and the plug subassembly, the upper end thereof being engaged with the setting tool, the lower end thereof having a plurality of fingers separated by slots, each finger thereof ending in a head at the tip, each head thereof being configured to engage the face of the release sleeve; c) installing the plug subassembly onto the setting tool by sliding the collet adapter through the progressively tapering inner diameter of the release sleeve thereby compressing and snapping the collet adapter thereof into an engaging position wherein a lower surface of each of the head engages the face, the plug subassembly and the collet adaptor together forming a downhole plug assembly; d) deploying the downhole plug assembly engaged with the setting tool downhole to a predetermined location; e) actuating a setting sleeve with a setting load, the sleeve thereof contacting the top element at a bottom end, thereby pushing the top element and setting the plug, wherein the anchoring system engages the plug with the casing and the sealing system seals the gap between the outer surface of the plug and the casing; and f) applying a load greater than the setting load thereby pulling the collet adapter, the fingers thereof radially expanding to securely engage the face thereby transferring the load to the release sleeve and then to the shearable fastening members causing the fastening members to shear off and the release sleeve thereof to release from the mandrel.
 12. The method as claimed in claim 11, wherein the receiving member is a hole, the hole thereof extending therethrough perpendicular to the longitudinal axis of the bore.
 13. The method as claimed in claim 11, wherein the receiving member is a circumferential groove on the external surface.
 14. The method as claimed in claim 11, wherein the plug is a frac plug.
 15. The method as claimed in claim 14, wherein the bore has a conical feature defined for seating a frac ball.
 16. The method as claimed in claim 11, wherein the plug further comprises of a bridge plug adapter seated within the bore thus converting the plug into a bridge plug.
 17. The method as claimed in claim 16, wherein the bridge plug adapter is threadably engaged with an inner surface of the mandrel.
 18. The method as claimed in claim 11, wherein the plug is made of composite material.
 19. The method as claimed in claim 11, wherein the shearable fastening members engaging the mandrel with the release sleeve shear off without leaving any debris within the bore of the mandrel.
 20. The method as claimed in claim 11, wherein the shearable fastening members are shearable screws. 